1. Field of the Invention
This invention relates generally to hollow core wall panels having acoustical absorbing properties through the use of the Helmholtz resonator principle, and more particularly to large panels having additional Helmholtz resonator structures retained within the cavity of the hollow core panel.
2. Description of the Prior Art
The literature teaches through fundamental theory and such U.S. Pat. Nos. as 2,933,146, 3,506,089, 3,837,426, 3,866,001, and 4,562,901 of the practicality of a broad concept of forming building structures through the use of acoustically hard materials such as concrete blocks which can be made to be sound absorbing through the use of the widely known principle of the Helmholtz resonator. Some of these inventions have proven to be commercially successful, though with certain disadvantages associates with their use in terms of cost relative to their non-absorptive counterparts. Furthermore, these inventions offer no advantage in terms of labor savings with regard to ordinary masonry blocks commonly used in the building industry. Finally, the nature of these sound absorbing blocks is such that their design cannot be easily tailored to meet specific design requirements but offer the basis of a product line built on a limited number of configurations and performance inherently limits the size of the cavity and the configuration of the penetrations, restricting the frequency bandwidth over which sound absorption by the block can be achieved. This invention seeks to escape these restrictions by utilizing the whole surface of the wall and the interior cavity formed by the wall surface as one integral cavity which can be tailored to suit the needs of the sound absorption.
The scientific literature teaches that the addition of sound absorption to the surface of noise barriers increases their effectiveness. For example, if highway noise barriers are made sound absorbing, these would be more effective in mitigating highway noise. Sound absorbing highway noise barriers have been constructed of hollow metal case structures with perforated panel facings on the traffic side of the barrier. Fibrous material inside the panels absorbs the sound with the perforated facing acting to protect the panels. These panels act merely on the basis of the fibrous sound absorbing material principle and not through the use of the Helmholtz resonator principle. Due to the use of metal as the primary structural material, these panels are relatively expensive as compared to conventional wood or masonry reflective wall noise barriers.
In addition, some have proposed perfectly hard or perfectly sound absorptive cylinders placed on top of the above highway noise barriers to increase the effectiveness of the barriers, but each of these constructions is very expensive.
It is therefore an object of this invention to provide a sound absorbing hollow core building wall panel for use in exterior and interior applications that can achieve improved absorption performance over pre-selected broadband frequency ranges.
At the same time, it is the purpose of this invention to take advantage of efficiencies achieved through the use of manufacturing and installation methods associated with molded, poured, or otherwise pre-manufactured hollow core building panels over the much smaller single block units. A typical approach by which these hollow core wall panels can be manufactured at a cost comparable to ordinary concrete wall products which are not sound absorbing as described in U.S. Pat. No. 5,369,930. However, the manufacturing process for sound absorbing hollow core wall panels need not be limited to the approach described in this patent. U.S. Pat. No. 5,369,930 is incorporated herein by reference in its entirety as if it were set forth fully herein.
It is an important object of the invention to provide a large hollow panel with a large cavity and orifices to provide a first sound absorbing resonator and a plurality of additional sound resonators held within the cavity for broadband sound absorption.
It is another important object of the invention to join hollow panels to each other to form a larder panel with perimeter means that provides a single large resonator.
A further object of this invention is to provide a hollow core panel such that the panel can also absorb sound energy incident upon both its front and rear external surfaces or its perimeter surfaces.
An additional object of this invention is to provide a hollow core panel such that the design and manufacture of the product can easily be adapted to meet specific performance goals should the need arise.
Another object of this invention is to provide a hollow core panel such that the design of the orifices is easily configured to meet aesthetic requirements.
Another object of this invention is to provide a hollow core panel such that the design may be applied to entirely new installations or to the modification of existing structures.
Yet another object is to provide a sound absorbing structural hollow core panel that can be readily manufactured and installed with a favorable cost of manufacturing and installation as compared to prior art building materials and methods of similar performance characteristics.